It is known to use an electrochemical cell for measuring the difference in oxygen potential between a bath of molten metal, such as iron or steel, and a reference. Such known devices are mounted on the end of a carrier such as a tube or rod.
In the course of numerous practical experiments with such known devices, I have found that the measurements were often uncertain. It was not possible to obtain measurements with sufficient reliability. As a result of further research, I have found that upon entrance of the measuring head into the bath of molten metal the character of uncertainty was due to failure resulting in thermal shock. The purpose of the present invention is to solve this difficulty in a practical manner without substantially increasing the cost or complicating the fabrication of the device.
U.S. Pat. Nos. 3,619,381 and 3,752,753 disclose oxygen sensors of different construction and recognize the problem of thermal shock. Applicant's solution of this problem differs materially from the solution disclosed in said patents.